Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/34—DC amplifiers in which all stages are DC-coupled
  • H03F3/343—DC amplifiers in which all stages are DC-coupled with semiconductor devices only
  • H03F3/345—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with field-effect devices
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/04—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only
  • H03F3/16—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only with field-effect devices
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
  • H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
  • H03F1/3217—Modifications of amplifiers to reduce non-linear distortion in single ended push-pull amplifiers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/30—Single-ended push-pull [SEPP] amplifiers; Phase-splitters therefor
  • H03F3/3001—Single-ended push-pull [SEPP] amplifiers; Phase-splitters therefor with field-effect transistors
  • H03F3/301—CMOS common drain output SEPP amplifiers
  • H03F3/3011—CMOS common drain output SEPP amplifiers with asymmetrical driving of the end stage

Definitions

• This invention relates to high voltage and power output circuits, and more particularly, to an improved cascaded configuration for a class AB MOS output stage.
• High voltage and high power output circuits may be manufactured from bipolar output stages or MOS structures.
• a typical class AB output stage utilizing MOS structures is shown in Fig. 1.
• Fig. 1 depicts a cascaded class AB buffer utilizing bipolar transistors and several diodes as shown. Notably, there are four static current paths 201-204, leading to increased power consumption. As stated above, minimization of power consumption is a goal in class AB output stages. Thus, the arrangement of Fig. 1 is suboptimal.
• Fig. 2 shows a class C Darlington output stage with biasing resistors utilizing
• Fig. 2 FET technology.
• the arrangement of Fig. 2 would appear to consume less power than that of Fig. 1 , owing to the fact that there are less current paths.
• transistors M3 and M4 see the load through biasing resistors Rl and R2.
• transistors M3 and M4 must be sized properly to prevent slowing down of the circuit. Often, this means utilizing larger transistors, with higher power consumption, than desirable. Thus, the larger transistors can make up for the reduction in current paths, and a relatively high power consuming device still results.
• crossover distortion In addition to the foregoing power consumption problem, another problem in output stages is that of crossover distortion.
• a prior art known technique of minimizing crossover distortion is to utilize a feedback loop to cancel such distortion.
• the implementation of such a feedback loop also results in added power consumption.
• the present invention includes a circuit having cascaded output stages utilizing three sets of FET devices. Of the three sets of FET devices, in a preferred embodiment, a first set includes four FETs, a second set includes a different four FETs, and a third set includes two FETs. Two of the transistors from the second set and the two transistors from the third set comprise one class AB stage, and the remaining two transistors from the second set and all four transistors from the first set comprise the second class AB stage.
• the two stages are cascaded in a manner that reduces the required size for the transistors as well as eliminating crossover distortion. The arrangement avoids such crossover distortion without the need for a feedback loop, thereby eliminating the additional components that would otherwise be required and also minimizing power dissipation.
• the circuit has the further advantage of minimizing current paths, and thus power consumption, while permitting smaller size transistors to be used, even to drive relatively highly capacitive output loads. Further advantages of the present invention will become clear from the following detailed description and drawings.
• Fig. 1 shows a exemplary prior art arrangement
• Fig. 2 depicts an additional prior art arrangement having the drawback of relatively high power consumption
• Fig. 3 shows an exemplary embodiment of the present invention utilizing ten FET devices.
• Fig. 3 shows an exemplary embodiment of the present invention utilizing ten FET devices. It is understood that the particular transistors utilized are not critical to the present invention, and that other types of active devices may be utilized.
• the exemplary embodiment of Fig. 3 comprises four FET devices 601-604 connected to the input power source.
• the source of FET 601 is connected as shown to the gate of FET 605, and the drain of FET 604 is connected to the gate of FET 608 as also shown.
• FETs 608, 605 and 601-604 constitute the equivalent of a single stage of a class AB output circuit.
• the remaining FETs 606, 607, 609 and 610 constitute a second output stage.
• the two output stages are connected at a junction between FET 605 and 606, and are also connected at the junction between FETs 607 and 608.
• FETs 606,607, 609 and 610 By driving the gates of FETs 606,607, 609 and 610 from a common source as shown, the aforementioned four transistors act as a single output stage. Moreover, since FETs 605 and 608 have their respective gates tied to the gates of FETs 601 and 604 respectively, FETs 605 and 608 are part of the first stage.
• the power is provided to the system from source 600 through series FET devices 601-604.
• the signal to be amplified is provided at point 615 as shown.
• the signal is then amplified through the consecutive AB stages and an output is seen at point 616.
• Fig. 4 permits smaller transistors utilized in the prior art arrangements or circuits with the same response times. The use of such smaller transistors provides for reduced input capacitance and thus, lower delay.
• the circuit does not generate significant crossover distortion, thereby eliminating the need for a feedback loop in most applications. This mode of operation thus reduces power consumption. It is also noted that the system has at most three current paths, unlike some prior art arrangements that include at least four such paths.
• the device may be powered by a voltage source or a current source.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (9)

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• 2002
  • 2002-05-28 US US10/156,248 patent/US6727758B2/en not_active Expired - Lifetime
• 2003
  • 2003-04-28 JP JP2004508503A patent/JP2005528056A/ja active Pending
  • 2003-04-28 AT AT03715264T patent/ATE460008T1/de not_active IP Right Cessation
  • 2003-04-28 AU AU2003219452A patent/AU2003219452A1/en not_active Abandoned
  • 2003-04-28 CN CN038120089A patent/CN1656673B/zh not_active Expired - Fee Related
  • 2003-04-28 EP EP03715264A patent/EP1518322B1/de not_active Expired - Lifetime
  • 2003-04-28 WO PCT/IB2003/001708 patent/WO2003100967A1/en not_active Ceased
  • 2003-04-28 KR KR10-2004-7019136A patent/KR20050007561A/ko not_active Ceased
  • 2003-04-28 DE DE60331544T patent/DE60331544D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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